With the advent of the Internet and a decline in computer prices, many people are communicating with one another through computers interconnected by networks. A number of different communication mediums (e.g., electronic mail (e-mail) and instant messaging (IM)) have been developed to facilitate such communications between computer users.
Unfortunately, because the costs of sending messages using these mediums are relatively low, computer users are being subjected to mass, unsolicted, commercial communications (colloquially known as spam). Those who send spam are typically referred to as spammers. Spam impacts both users and communication service providers. For users, spam can be disruptive, annoying, and time consuming. For a service provider, spam represents tangible costs in terms of storage and bandwidth usage. These costs may be substantial when large numbers of spam are sent.